Carbon catalyst, method for manufacturing the carbon catalyst, and electrode and battery using the carbon catalyst

ABSTRACT

A method of manufacturing a carbon catalyst according to the present invention includes: a first step involving heating a raw material containing a resin and a metal to carbonize the resin so that a carbon catalyst is obtained; a second step involving subjecting the carbon catalyst to a treatment for removing the metal; and a third step involving subjecting the carbon catalyst that has been subjected to the treatment to a heat treatment to improve an activity of the carbon catalyst.

TECHNICAL FIELD

The present invention relates to a carbon catalyst and a method ofmanufacturing the carbon catalyst, and an electrode and a battery eachusing the carbon catalyst, in particular, a carbon catalyst that canreplace a precious metal catalyst such as platinum or palladium.

BACKGROUND ART

A polymer electrolyte fuel cell (PEFC) can operate in a low-temperatureregion and has high energy conversion efficiency, and a time periodrequired for its startup is short. In addition, the system of the PEFCcan be made small and lightweight. Accordingly, the PEFC has beenexpected to find applications in power sources for electric vehicles,portable power sources, and household co-generation systems.

However, large amounts of platinum catalysts are used in the PEFC. Theuse of the platinum catalysts causes an increase in cost, which is onefactor that may inhibit the widespread use of the PEFC. In addition, aconcern has been raised in that restriction is imposed on the PEFC interms of platinum reserves.

In view of the foregoing, the development of a novel catalyst that canreplace the platinum catalyst has been advanced. That is, for example, acarbon catalyst obtained by imparting a catalytic activity to a carbonmaterial itself has been proposed (see, for example, JP 2007-026746 A,JP 2007-207662 A and JP 2008-282725 A).

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP 2007-026746 A

Patent Document 2: JP 2007-207662 A

Patent Document 3: JP 2008-282725 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, no catalyst having a high activity sufficient to replace theplatinum catalyst in the PEFC has been put into practical use yet.

The present invention has been made in view of the above-mentionedproblems, and an object of the present invention is to provide a carboncatalyst having an excellent activity and a method of manufacturing thecarbon catalyst, and an electrode and a battery each using the carboncatalyst.

Means for Solving the Problems

A carbon catalyst according to one embodiment of the present inventionfor solving the above-mentioned problems is characterized by including acarbon structure, in which the carbon structure is formed of a carbonnetwork plane in which, in a distribution of crystallite sizes La of 7.2nm or less, a ratio of crystallite sizes of 1 to 5 nm is 10% or more,and a ratio of crystallite sizes in excess of 5 nm is 60% or less.According to the present invention, there can be provided a carboncatalyst having an excellent activity.

A carbon catalyst according to one embodiment of the present inventionfor solving the above-mentioned problems is characterized by including acarbon structure, in which the carbon structure is formed of a carbonnetwork plane in which, in a distribution of crystallite sizes La of 7.2nm or less, a ratio of crystallite sizes of 1 to 5 nm is 10% or more,and a ratio of crystallite sizes less than 1 nm is 70% or less.According to the present invention, there can be provided a carboncatalyst having an excellent activity.

Further, in the distribution of the crystallite sizes La, a ratio ofcrystallite sizes of 2 to 5 nm may be 80% or more, and a ratio ofcrystallite sizes of less than 2 nm may be 10% or less. In addition, inthe distribution of the crystallite sizes La, a ratio of crystallitesizes of 3 to 5 nm may be 70% or more, and a ratio of crystallite sizesof less than 3 nm may be 20% or less. Thus, there can be more reliablyprovided a carbon catalyst having an excellent activity.

Further, the carbon structure may include a carbon structure formed byheating a raw material containing a resin and a metal to carbonize theresin. Thus, there can be reliably provided a carbon catalyst having anexcellent activity.

An electrode according to one embodiment of the present invention forsolving the above-mentioned problems is characterized by carrying anyone of the above-mentioned carbon catalysts. According to the presentinvention, there can be provided an excellent electrode carrying acarbon catalyst having an excellent activity.

A battery according to one embodiment of the present invention forsolving the above-mentioned problems is characterized by including theabove-mentioned electrode. According to the present invention, there canbe provided an excellent battery including an electrode carrying acarbon catalyst having an excellent activity.

A method of manufacturing a carbon catalyst according to one embodimentof the present invention for solving the above-mentioned problems ischaracterized by including: a first step involving heating a rawmaterial containing a resin and a metal to carbonize the resin so that acarbon catalyst is obtained; a second step involving subjecting thecarbon catalyst to a treatment for removing the metal; and a third stepinvolving subjecting the carbon catalyst that has been subjected to thetreatment to a heat treatment to improve an activity of the carboncatalyst. According to the present invention, there can be provided amethod of manufacturing a carbon catalyst having an excellent activity.

Further, the heat treatment may be performed by heating the carboncatalyst at a temperature in a range of 300 to 1,500° C. Further, theheat treatment may be performed by heating the carbon catalyst at atemperature equal to or lower than a temperature at which the rawmaterial is heated in the first step. Further, the carbon catalyst maybe subjected to the treatment in the second step by washing the carboncatalyst with an acid. Further, the metal may include a transitionmetal. Thus, a carbon catalyst having an excellent activity can be moreeffectively manufactured.

A carbon catalyst according to one embodiment of the present inventionfor solving the above-mentioned problems is characterized by beingmanufactured by any one of the above-mentioned methods. According to thepresent invention, there can be provided a carbon catalyst having anexcellent activity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram illustrating main steps in an exampleof a method of manufacturing a carbon catalyst according to oneembodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a relationship between avoltage and a current measured for the carbon catalyst according to oneembodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating an example of the resultsof the evaluation of the carbon catalyst according to one embodiment ofthe present invention for its oxygen reduction activity.

FIG. 4 is an explanatory diagram illustrating another example of theresults of the evaluation of the carbon catalyst according to oneembodiment of the present invention for its oxygen reduction activity.

FIG. 5 is an explanatory diagram illustrating still another example ofthe results of the evaluation of the carbon catalyst according to oneembodiment of the present invention for its oxygen reduction activity.

FIG. 6 is an explanatory diagram for a benzene-coronene base model usedin the analysis of the carbon catalyst according to one embodiment ofthe present invention for the distribution of the crystallite sizes La.

FIG. 7 is an explanatory diagram illustrating an example of the resultsof the analysis of the carbon catalyst according to one embodiment ofthe present invention for the distribution of the crystallite sizes La.

FIG. 8 is an explanatory diagram illustrating another example of theresults of the analysis of the carbon catalyst according to oneembodiment of the present invention for the distribution of thecrystallite sizes La.

FIG. 9 is an explanatory diagram illustrating a ratio of each range ofthe crystallite sizes La in the distribution of the crystallite sizes Laobtained for the carbon catalyst according to one embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, one embodiment of the present invention is described. Itshould be noted that the present invention is not limited to any exampledescribed in this embodiment.

FIG. 1 is an explanatory diagram illustrating main steps in an exampleof a method of manufacturing a carbon catalyst according to thisembodiment (hereinafter referred to as “Manufacturing Method”). Asillustrated in FIG. 1, the Manufacturing Method includes a rawmaterial-preparing step S1, a carbonizing step S2, a metal-removing stepS3, and a heat treatment step S4.

In the raw material-preparing step S1, a raw material containing a resinand a metal is prepared. The resin is not particularly limited as longas the resin is a polymer material that can be carbonized in thecarbonizing step S2 to be described later. That is, for example, athermosetting resin or thermoplastic resin that can be carbonized can beused. Specific examples which can be used include polyvinylpyridinepolyacrylonitrile, a chelate resin, cellulose, carboxymethylcellulose,polyvinylalcohol, polyarylate, a polyfurfuryl alcohol, a furan resin, aphenol resin, a phenol-formaldehyde resin, polyimidazole, a mealmineresin, an epoxy resin, pitch, brown coal, polyvinylidene chloride,polycarbodiimide, lignin, anthracite, biomass, a protein, humic acid,polyimide, polyaniline, polypyrrole, nitrogen-containing ligandpolymerized articles, and metallic ligand compounds. One kind of resinmay be used alone, or two or more kinds thereof may be used incombination.

In addition, the resin can be a polymer ligand that can coordinate tothe metal contained in the raw material. That is, in this case, a resincontaining one or more ligand atoms in its molecule is used.Specifically, for example, there can be used a resin containing, asligand atoms in its molecule, one or more of one kind, or two or morekinds, selected from the group consisting of a nitrogen atom, aphosphorous atom, an oxygen atom, and a sulfur atom. That is, forexample, there can be used a resin containing, as ligand groups, in itsmolecule, one or more of one kind, or two or more kinds, selected fromthe group consisting of an amino group, a phosphino group, a carboxylgroup, and a thiol group.

In addition, when the resin serving as a ligand is used, the rawmaterial contains a complex formed as a result of the coordination ofthe resin to the metal. Therefore, the resin and the metal can beintegrally and efficiently dispersed in the raw material.

Further, as the resin serving as a polymer ligand, a resin containing,as ligand atoms, one or more nitrogen atoms in its molecule can bepreferably used. Specifically, for example, there can be preferably usedone kind, or two or more kinds, selected from the group consisting ofpolyvinyl pyridine, a salen polymer, polypyrrole, polyvinyl pyrrole,3-methyl polypyrrole, polyvinyl carbazole, polyamide, polyaniline,polybismaleimide, and polyamideimide.

In this case, the resin, the metal, and the nitrogen atoms can beintegrally and efficiently dispersed in the raw material. In addition,the nitrogen atoms in the resin exert a nitrogen-doping effect in thecarbon catalyst manufactured by the Manufacturing Method, and hence canimprove the activity of the carbon catalyst.

In addition to such resin, a resin containing one or more nitrogen atomsin its molecule can also be preferably used. Specifically, for example,polyacrylonitrile (PAN), a urea resin oligomer, and a mealmine resin canbe used. In this case, the resin and the nitrogen atoms can beintegrally and efficiently dispersed in the raw material.

In addition, when a resin poor in thermosetting property is used, theresin may be made infusible. This operation allows the structure of theresin to be maintained even at a temperature equal to or higher than amelting point or softening point inherent in the resin. The resin can bemade infusible by a known method.

The form of a mixture of the thermoplastic resin and the metal or theform of a metal complex of the thermoplastic resin is not particularlylimited as long as the activity of the carbon catalyst manufactured bythe Manufacturing Method is not impaired. Examples of the form include asheet form, a fiber form, a block form, and a particle form.

The metal is not particularly limited as long as the activity of thecarbon catalyst manufactured by the Manufacturing Method is notimpaired. That is, for example, a transition metal can be preferablyused as the metal, and a metal belonging to the fourth period of Groups3 to 12 in the periodic table can be particularly preferably used as themetal.

One kind of those metals may be used alone, or two or more kinds thereofmaybe used in combination. Specifically, for example, there can bepreferably used one kind, or two or more kinds, selected from the groupconsisting of cobalt, iron, nickel, manganese, zinc, and copper. Ofthose, cobalt or iron can be particularly preferably used.

In addition, the metal can be used in the form of a simple substance ofthe metal or a compound of the metal. For example, a metal salt, a metalhydroxide, a metal oxide, a metal nitride, a metal sulfide, a metalcarbide, or a metal complex can be preferably used as the metalcompound, and a metal chloride, the metal oxide, or the metal complexcan be particularly preferably used as the metal compound.

In addition, the raw material may contain a conductive carbon materialfor imparting conductivity to the carbon catalyst. A carbon materialhaving conductivity can be used as the conductive carbon materialwithout any particular limitation. That is, for example, a carbonmaterial which has conductivity but has no catalytic activity by itselfcan be used. The shape of the conductive carbon material is notparticularly limited, and for example, a particulate or fibrous materialcan be used.

When the fine particles of the conductive carbon material are used, theaverage particle diameter of the fine particles preferably falls withinthe range of 3 to 100 nm. In addition, the BET specific surface area ofthe fine particles preferably falls within the range of 100 to 2,000m²/g.

Specifically, for example, there can be preferably used, as theconductive carbon material, one kind, or two or more kinds, selectedfrom the group consisting of carbon black, carbon nanotube, carbonnanofiber, graphite, activated carbon, glass-like carbon, carbon fiber,and fullerene. For example, Ketjen Black, Vulcan, Toka Black, or DenkaBlack can be used as carbon black.

In the raw material-preparing step S1, the raw material can be preparedby mixing such resin and metal as described above. That is, the rawmaterial can be, for example, a mixed powder of the metal complex of theresin and the fine particles of the conductive carbon material. A methodof mixing the contents of the raw material is not particularly limited.That is, one kind of mixing method such as powder mixing, solventmixing, supercritical fluid mixing, and electrolytic polymerizationcoating may be employed alone, or two or more kinds thereof may beemployed in combination.

When a conductive carbon material is used, for example, a content of theconductive carbon material in the raw material preferably falls withinthe range of 1 to 85 mass %, and more preferably falls within the rangeof 5 to 50 mass %. When the content of the conductive carbon material isless than 1 mass %, sufficient conductivity cannot be imparted to thecarbon catalyst manufactured by the Manufacturing Method in some cases.In addition, when the content of the conductive carbon material exceeds85 mass %, the activity of the carbon catalyst manufactured by theManufacturing Method may reduce instead.

In the carbonizing step S2, the raw material prepared as described aboveis heated to carbonize the resin so that a carbon catalyst is obtained.That is, the raw material is held at such a predetermined temperaturethat the resin in the raw material can be carbonized (carbonizationtemperature).

The carbonization temperature is not particularly limited, and can beappropriately set depending on conditions such as the melting point anddecomposition point of the resin. That is, for example, thecarbonization temperature can be set to fall within the range of 300 to1,500° C., can be preferably set to fall within the range of 500 to1,200° C., can be more preferably set to fall within the range of 600 to1, 200° C., and can be particularly preferably set to fall within therange of 700 to 1,200° C.

In addition, a rate of temperature increase can be set to fall withinthe range of 0.5 to 300° C./min. In addition, for example, the timeperiod for which the raw material is held at the above-mentionedcarbonization temperature can be set to fall within the range of 5 to180 minutes, and can be preferably set to fall within the range of 20 to120 minutes. When the holding time is less than 5 minutes, the resincannot be uniformly carbonized in some cases. In addition, when theholding time exceeds 180 minutes, the catalytic activity maysignificantly reduce owing to the disappearance of an edge surface of acarbon network plane. In addition, the carbonization treatment ispreferably performed in a stream of an inert gas such as nitrogen.

In the carbonizing step S2, a carbon catalyst having a carbon structureformed by the carbonization of the resin can be obtained. It should benoted that the carbon structure includes a carbon network plane formedas a result of two-dimensional binding and spread of the hexagonalnetwork planes of carbon. A defective portion such as an edge portion orbent portion of the carbon network plane may serve as an active site ofthe carbon catalyst. The carbon structure can be a structure in which aplurality of carbon network planes are laminated.

The metal-removing step S3 involves subjecting the carbon catalystobtained in the above-mentioned carbonizing step S2 to a treatment forremoving the metal. The metal-removing treatment can remove the metal inthe carbon catalyst or reduce the content of the metal in the carboncatalyst.

A method of removing the metal is not particularly limited. That is, forexample, a washing treatment with an acid or an electrolytic treatmentcan be employed. When the washing with an acid is performed, boilingacid may be used. For example, hydrochloric acid can be preferably usedas the acid.

The heat treatment step S4 involves subjecting the carbon catalyst thathas been subjected to the metal-removing treatment in theabove-mentioned metal-removing step S3 to a heat treatment to improvethe activity of the carbon catalyst. The heat treatment is performed byholding the carbon catalyst at a predetermined temperature (heattreatment temperature). For example, the heat treatment temperature canbe a temperature in the range of 300 to 1,500° C., and is set topreferably 400° C. or more, more preferably 600° C. or more, andparticularly preferably 700° C. or more. Performing the heat treatmentat 600° C. or more, or 700° C. or more can effectively improve theactivity of the carbon catalyst. In addition, the heat treatmenttemperature is set to preferably 1,200° C. or less, more preferably1,000° C. or less.

The range of the heat treatment temperature can be a range obtained byarbitrarily combining those lower and upper Limits. That is, forexample, the heat treatment temperature can be set to fall within therange of 400 to 1,200° C., can be preferably set to fall within therange of 600 to 1,200° C., can be more preferably set to fall within therange of 700 to 1,200° C., and can be particularly preferably set tofall within the range of 700 to 1,000° C. In addition, for example, thetime period for which the carbon catalyst is held at any such heattreatment temperature can be set to fall within the range of 10 minutesto 5 hours, and can be preferably set to fall within the range of 30minutes to 2 hours. A rate of temperature increase can be set to fallwithin the range of, for example, 0.5 to 1,000° C./min.

As described above, the heat treatment is preferably performed at atemperature lower than a heating temperature generally adopted in theso-called graphitization treatment. That is, the heat treatment can beperformed by, for example, heating the carbon catalyst at a heattreatment temperature equal to or lower than the temperature at whichthe raw material is heated in the carbonizing step S2 or at a heattreatment temperature lower than the temperature.

Specifically, for example, when the heating temperature in thecarbonization treatment falls within the range of 600 to 1,200° C. orwhen the heating temperature falls within the range of 700 to 1,200° C.,the heat treatment can be performed at a heat treatment temperaturewithin the range and equal to or lower than the heating temperature orat a heat treatment temperature lower than the heating temperature.

Such heat treatment can result in effective formation of, for example,structural defects serving as active sites on the surface of the carboncatalyst. In addition, the heat treatment can remove, for example, aninert metal component remaining in a trace amount in the carbon catalystafter the metal-removing treatment. Therefore, a carbon catalyst havingan additionally high activity as a result of effective exposure of theactive sites can be obtained. As described above, according to theManufacturing Method, a carbon catalyst excellent in catalyticactivities such as an oxygen reduction activity can be manufactured.

In addition, the Manufacturing Method can include the step ofintroducing (doping) nitrogen atoms or boron atoms into the carboncatalyst. A method of introducing the nitrogen atoms or boron atoms intothe carbon catalyst is not particularly limited. That is, when thecarbon catalyst is doped with the nitrogen atoms, for example, a vaporphase doping method such as an ammo-oxidation method or a CVD method, aliquid phase doping method, or a vapor phase-liquid phase doping methodcan be employed.

Specifically, for example, in the vapor phase doping method, thenitrogen atoms can be introduced into the surface of the carbon catalystby: mixing the carbon catalyst and a nitrogen source such as ammonia,melamine, or acetonitrile; and holding the mixture under an atmosphereof an inert gas such as nitrogen, argon, or helium and air at atemperature in the range of 550 to 1,200° C. for a time period in therange of 5 to 180 minutes or treating the mixture with heat in an NOxgas. As a result of the introduction of the nitrogen atoms, the nitrogenatoms can be introduced into, for example, the hexagonal network planestructures of the carbon structure to form pyrrole-type,graphene-substituted, pyridine-type, pyridone-type, or oxidizedstructures.

A carbon catalyst according to this embodiment (hereinafter referred toas “Catalyst”) is a carbon catalyst manufactured by providing a carbonmaterial itself with a catalytic activity, and can be efficientlymanufactured by the Manufacturing Method described above.

The Catalyst is a carbon catalyst having a carbon structure including acarbon network plane. The carbon structure can be formed by, forexample, heating a raw material containing a resin and a metal, tocarbonize the resin as described above. In addition, the carbonstructure is formed so as to include carbon network planes in whichdefective portions such as edge portions and bent portions are formed asactive sites.

That is, for example, in the case where the Catalyst is manufactured bycarbonizing a raw material containing a thermosetting resin and a metal(e.g., a raw material containing a metal complex of the thermosettingresin), the Catalyst can have a turbostratic structure (nanoshellstructure) similar to a graphite structure laminated and developed likean onion around a fine particle of the metal. In this case, in thecarbon catalyst, an edge portion of a carbon network plane in theturbostratic structure or a bent portion of the carbon network planeprobably serves as an active site so that the catalytic activity of thecarbon material itself may be educed.

In addition, for example, in the case where the Catalyst is manufacturedby carbonizing a raw material containing a thermoplastic resin, a metal,and a conductive carbon material (e.g., a raw material containing ametal complex of the thermoplastic resin and the conductive carbonmaterial), the Catalyst can have the conductive carbon material and acarbon structure that coats the surface of the conductive carbonmaterial. In this case, the carbon structure is formed into a film shapealong the surface of the conductive carbon material to serve as thecoating of the conductive carbon material. That is, the Catalyst has aconductive carbon material portion as the so-called carrier (basematerial) and a carbon structure portion (carbonized layer) includingactive sites, the carbon structure portion being formed on the surfaceof the conductive carbon material. The carbon structure can be formed byheating the raw material in the process of the carbonization to coat thesurface of the conductive carbon material with the molten thermoplasticresin, and to carbonize the thermoplastic resin on the surface of theconductive carbon material.

The Catalyst has, for example, an oxygen reduction activity as acatalytic activity. That is, the Catalyst can effectively catalyze, forexample, an oxygen reduction reaction in an electrode for a fuel cell.

The Catalyst can be evaluated for its oxygen reduction activity in termsof, for example, an oxygen reduction-starting potential. That is, theoxygen reduction-starting potential of the Catalyst can be set to fallwithin the range of, for example, 0.7 V or more versus a normal hydrogenelectrode (vs. NHE) and 1.2 V or less vs. NHE when the evaluation isperformed by regarding the potential as the voltage at which a reductioncurrent of −10 μA/cm² flows. In addition, for example, the oxygenreduction-starting potential can be set to 0.75 V or more, can bepreferably set to 0.76 V or more, and can be more preferably set to 0.77V or more.

It should be noted that the oxygen reduction-starting potential can bedetermined on the basis of, for example, data showing a relationshipbetween the voltage and a current obtained by sweeping and applying apotential with a rotating ring-disk electrode apparatus having a workingelectrode wherein the Catalyst has been coated.

In addition, the Catalyst can be evaluated for its catalytic activity interms of, for example, the number of electrons involved in an oxygenreduction reaction. In an oxygen reduction reaction catalyzed by theCatalyst, the number of electrons involved in the reaction is calculatedas the number of electrons involved in the reduction reaction permolecule of oxygen.

That is, for example, in such a reaction where water is produced fromprotons and oxygen in the cathode electrode (air electrode) of a fuelcell, four electrons are theoretically involved in a reduction reactionfor one molecule of oxygen. In actuality, however, a reaction in whichhydrogen peroxide is produced as a result of the involvement of twoelectrons in a reduction reaction for one molecule of oxygen also occursin parallel.

Therefore, it can be said that in the oxygen reduction reaction of thecathode electrode, the number of electrons involved in a reductionreaction for one molecule of oxygen is preferably as close to four aspossible because an additionally large quantity of current can beobtained, the generation of hydrogen peroxide can be suppressed, and anenvironmental load can be reduced.

In this regard, according to the Catalyst, the number of electronsinvolved in the oxygen reduction reaction can be set to fall within therange of 3.5 to 4, can be preferably set to 3.6 or more, and can be morepreferably set to 3.8 or more.

In addition, the Catalyst can have a characteristic distribution ofcrystallite sizes La of the carbon network planes of which its carbonstructure is formed. It should be noted that the term “crystallite sizeLa” refers to the spread of a carbon network plane in an a-axisdirection.

That is, in the distribution of the crystallite sizes La of 7.2 nm orless of the carbon network planes of which the carbon structure of theCatalyst is formed, a ratio of crystallite sizes of 1 to 5 nm can be setto 10% or more, and a ratio of crystallite sizes in excess of 5 nm canbe set to 60% or less. Further, the ratio of the crystallite sizes of 1to 5 nm can be preferably set to 20% or more, can be more preferably setto 30% or more, and can be particularly preferably set to 40% or more.In addition, the ratio of the crystallite sizes in excess of 5 nm can bepreferably set to 50% or less, and can be more preferably set to 40% orless. The ratio of the crystallite sizes of 1 to 5 nm and the ratio ofthe crystallite sizes in excess of 5 nm in the distribution of thecrystallite sizes La can be obtained by arbitrarily combining theabove-mentioned ranges.

Further, in the distribution of the crystallite sizes La of 7.2 nm orless of the carbon network planes of which the carbon structure of theCatalyst is formed, a ratio of crystallite sizes of 1 to 5 nm can be setto 10% or more, and a ratio of crystallite sizes less than 1 nm can beset to 70% or less. Further, the ratio of the crystallite sizes of 1 to5 nm can be preferably set to 20% or more, can be more preferably set to30% or more, and can be particularly preferably set to 40% or more. Inaddition, the ratio of the crystallite sizes less than 1 nm can bepreferably set to 60% or less. The ratio of the crystallite sizes of 1to 5 nm and the ratio of the crystallite sizes less than 1 nm in thedistribution of the crystallite sizes La can be obtained by arbitrarilycombining the above-mentioned ranges.

Such distribution of the crystallite sizes La can be determined by, forexample, Diamond's method on the basis of the results of X-raydiffraction measurement. The Diamond's method is a method proposed byDiamond in 1956 for the evaluation of carbon network planes in a samplehaving a relatively small network plane size such as coal or pitch fortheir average size and distribution (see, for example, R. Diamond, Ph.D.Dissertation, University of Cambridge, England, 1956, R. Diamond, Acta.Cryst. 10 (1957) 359-363., R. Diamond, Acta. Cryst. 11 (1958) 129-138.,and R. Diamond, Phil. Trans. Roy. Soc. London A252 (1960) 193-223.).Specifically, the method is a method of evaluating, under the assumptionthat a carbon sample whose structure is unknown is an aggregate ofseveral kinds of model carbon network planes whose structures are known,the distribution of network plane sizes, the method involving:representing a measured eleven-band intensity in an X-ray diffractionprofile obtained for the sample as the sum of the products of thetheoretical X-ray scattering intensities of predetermined model networkplanes and weight fractions; and determining the respective weightfractions by the least-square method (see, for example, HiroyukiFUJIMOTO, Carbon, 228 (2007) 185-194.).

An electrode according to this embodiment (hereinafter referred to as“Electrode”) is an electrode that carries the Catalyst described above.That is, the Electrode can be formed so as to have a predeterminedelectrode base material and the Catalyst carried on the electrode basematerial.

The Electrode can be, for example, an electrode for a fuel cell. Morespecifically, the Electrode can be, for example, an electrode for apolymer electrolyte fuel cell (PEFC). That is, in this case, theCatalyst can be an electrode catalyst for a fuel cell, can be preferablyan electrode catalyst for a PEFC, and can be particularly preferably acathode electrode catalyst for a PEFC.

A battery according to this embodiment (hereinafter referred to as“Battery”) is a battery having the above-mentioned Electrode. That is,for example, the Battery can be a fuel cell and can be preferably a PEFCas described above.

More specifically, for example, when the Battery is a PEFC, the Batterycan have a membrane-electrode assembly (MEA) in which a polymerelectrolyte membrane, and a cathode electrode (positive electrode, airelectrode) and an anode electrode (negative electrode, fuel electrode)formed on one side, and the other side, of the polymer electrolytemembrane, are respectively integrated, and the cathode electrode cancarry the Catalyst.

Next, specific examples according to this embodiment are described.

EXAMPLE 1

After 1.5 g of vinyl pyridine had been dissolved in 20 mL ofdimethylformamide, polymerization was performed at 70° C. over 5 days.Thus, polyvinyl pyridine was obtained. 0.65 Gram of iron chloridehexahydrate was added to the polyvinyl pyridine, and then the mixturewas stirred at room temperature for 24 hours. Thus, a polyvinyl pyridineiron complex was obtained.

Ketjen black (EC600JD, Lion Corporation) was added to the complex, andthen the contents were mixed with a mortar. Thus, a raw materialcontaining the polyvinyl pyridine iron complex and the ketjen black, andcontaining the ketjen black at 50 wt %, was obtained.

In addition, a raw material containing a cobalt complex of the polyvinylpyridine and the ketjen black, and containing the ketjen black at 50 wt%, was obtained by using cobalt chloride hexahydrate instead of theabove-mentioned iron chloride hexahydrate.

Next, those raw materials were each subjected to a carbonizationtreatment. That is, first, the raw materials prepared as described abovewere each loaded into a quartz tube. Next, the quartz tube was placed inan ellipsoidal reflection-type infrared gold image furnace, and thennitrogen purge was performed for 20 minutes.

Then, heating was started, and the temperature of the gold image furnacewas increased from room temperature to 800° C. under a nitrogenatmosphere over 1.5 hours. After that, the quartz tube was held at 800°C. for 1 hour. A composition containing a carbon catalyst was obtainedby such carbonization treatment.

Further, the composition thus obtained was pulverized with a planetaryball mill (P-7, Fritsch Japan Co, Ltd.) in which silicon nitride ballseach having a diameter of 1.5 mm had been set at a rotational speed of800 rpm for 60 minutes. The pulverized composition was taken out, andthe fine particles of the carbon catalyst that had passed a sieve havingan aperture of 105 μm were recovered.

Further, the carbon catalyst obtained as described above was subjectedto an acid washing treatment for removing a metal. That is, 37% HCl wasadded to the carbon catalyst, and then the mixture was stirred for 2hours. After that, the mixture was left at rest, and then thesupernatant was decanted. The foregoing operation was performed threetimes. Further, suction filtration was performed, and then washing withdistilled water was performed. Next, boiling was performed. Thus, twokinds of carbon catalysts (a PVP/Fe/KB catalyst and a PVP/Co/KBcatalyst) each subjected to a metal-removing treatment were obtained.

In addition, part of the PVP/Fe/KB catalyst obtained as described abovewas subjected to a heat treatment. That is, the PVP/Fe/KB catalyst wasloaded into a quartz tube, and then the quartz tube was placed in anellipsoidal reflection-type infrared gold image furnace.

Then, the quartz tube was held in the infrared gold image furnace undera nitrogen atmosphere at 400° C., 700° C., or 1,000° C. for 1 hour.Thus, three kinds of carbon catalysts (a PVP/Fe/KB (H400) catalyst, aPVP/Fe/KB (H700) catalyst, and a PVP/Fe/KB (H1000) catalyst) subjectedto heat treatments at three different temperatures were obtained.

EXAMPLE 2

10 Grams of 8-quinolinol (oxine), 10 g of formaldehyde, and 1 g ofoxalic acid dihydrate were loaded into an eggplant flask having a volumeof 100 mL, and then the mixture was refluxed at 100° C. overnight. Next,5.5 mL of 1-M HCl were added to the resultant, and then the mixture wassimilarly refluxed overnight. The resultant solid was subjected tosuction filtration, washed with distilled water three times, and driedin a vacuum overnight. Thus, a polymer (Q polymer) was obtained.

Meanwhile, 8-quinolinol and phenol were mixed at such a ratio that themolar fraction of phenol in a polymer to be obtained was 70%. Theresultant mixture was loaded into a 100-mL eggplant flask in such anamount that the total amount of 8-quinolinol and phenol was 0.1 mol.Further, 0.1 mol of formaldehyde was added to the mixture, and then thecontents were uniformly mixed while the eggplant flask was warmed with ahot water bath at 100° C. One gram of oxalic acid dihydrate was loadedinto the eggplant flask, and then the whole was refluxed at 100° C.overnight. Further, 5.5 mL of 1-M HCl were added to the resultant, andthen the mixture was similarly refluxed overnight. The resultantcomposition was subjected to suction filtration, washed with distilledwater three times, and dried in a vacuum overnight. Thus, a polymer(Q-Ph polymer) was obtained.

3.3 Grams of each of the two kinds of polymers thus obtained were takenand dissolved in 100 mL of DMF. A solution prepared by dissolving 2.7 gof cobalt (II) chloride in 50 mL of DMF was added to the resultantsolution, and then the mixed solution was left at rest overnight. Themixed solution was dried in a vacuum with an evaporator (90° C.)overnight. The resultant composition was washed in a Soxhlet extractorwith ethanol for one day, and further, was dried in a vacuum overnight.Thus, two kinds of polymer cobalt complexes (a Q/Co complex and aQ-Ph/Co complex) were obtained.

Ketjen black (EC600JD, Lion Corporation) was added to each of the twokinds of polymer cobalt complexes thus obtained, and then the contentswere mixed with a mortar. Thus, two kinds of raw materials eachcontaining the Q/Co complex or the Q-Ph/Co complex, and the ketjenblack, and containing the ketjen black at 50 wt % were obtained.

Each of the two kinds of raw materials thus prepared was heated with aninfrared image furnace under a nitrogen atmosphere to 1,000° C. at arate of temperature increase of 10° C./min, and was then carbonized bybeing held at 1,000° C. for 1 hour. The resultant composition was groundwith a mortar, and then fine particles each having a particle diameterof 106 μm or less that had passed a sieve having an aperture of 106 μmwere recovered as a carbon catalyst.

Further, the carbon catalyst obtained as described above was subjectedto an acid washing treatment for removing cobalt. That is, 37% HCl wasadded to the carbon catalyst, and then the mixture was stirred for 2hours. After that, the mixture was left at rest, and then thesupernatant was decanted. The foregoing operation was performed threetimes. Further, after suction filtration was performed on the carboncatalyst, washing with distilled water was performed, and then boilingwas performed. Thus, two kinds of carbon catalysts (a Q/Co/KB catalystand a Q-Ph/Co/KB catalyst) each subjected to a metal-removing treatmentwere obtained.

EXAMPLE 3

3.275 Grams of a phenol resin (Gun Ei Chemical Industry Co., Ltd.) wereadded to 300 mL of acetone, and were then dissolved by being irradiatedwith an ultrasonic wave. Further, 1.0 g of a cobalt phthalocyaninecomplex (TOKYO CHEMICAL INDUSTRY CO., LTD.) was added to the solution,and then the solvent was removed with a rotary evaporator at 40 ° C.while an ultrasonic wave was applied. After that, the remainingcomposition was dried in a vacuum at a temperature of 80° C. for 24hours. Thus, a cobalt phthalocyanine complex containing a phenol resinwas synthesized.

The cobalt phthalocyanine complex thus prepared was loaded into a quartztube, and then nitrogen gas purge was conducted on the quartz tube for20 minutes in an ellipsoidal reflection-type infrared gold imagefurnace. Then, heating was started, and the temperature of the goldimage furnace was increased from room temperature to 800° C. at a rateof temperature increase of 10° C./min. After that, the quartz tube washeld at 800° C. for 1 hour. A carbon catalyst was obtained by suchcarbonization treatment.

Further, the carbon catalyst thus obtained was subjected to an acidwashing treatment for removing cobalt. That is, 37% HCl was added to thecarbon catalyst, and then the mixture was stirred for 2 hours. Afterthat, the mixture was left at rest, and then the supernatant wasdecanted. The foregoing operation was performed three times. Further,after suction filtration was performed on the carbon catalyst, washingwith distilled water was performed, and then boiling was performed.Thus, a carbon catalyst (a Pc/Co catalyst) subjected to a metal-removingtreatment was obtained.

In addition, part of the Pc/Co catalyst thus obtained was subjected to aheat treatment. That is, the Pc/Co catalyst was loaded into a quartztube, and then the quartz tube was placed in an ellipsoidalreflection-type infrared gold image furnace. Then, the quartz tube washeld in the infrared gold image furnace under a nitrogen atmosphere at400° C., 700° C., or 1,000° C. for 1 hour. Thus, three kinds of carboncatalysts (a Pc/Co (H400) catalyst, a Pc/Co (H700) catalyst, and a Pc/Co(H1000) catalyst) subjected to heat treatments at three differenttemperatures were obtained.

EXAMPLE 4

The five kinds of carbon catalysts obtained in Example 1, the two kindsof carbon catalysts obtained in Example 2, and the four kinds of carboncatalysts obtained in Example 3 were each evaluated for their oxygenreduction activity. That is, first, 5 mg of a powdery carbon catalystwere weighed, and then 50 μL of a binder solution (Nation (registeredtrademark), Du Pont Co., Ltd.), 150 μL of water, and 150 μL of ethanolwere added in appropriate amounts to the carbon catalyst. The mixedsolution was prepared as catalyst slurry.

Next, a trace amount of the catalyst slurry was sucked with a pipette,and was then coated on a disk electrode (having a diameter of 5 mm) of arotating ring-disk electrode apparatus (RRDE-l SC-5, Nikko Keisoku Co.,Ltd.), followed by drying. Thus, a working electrode was manufactured. Aplatinum electrode was used as a ring electrode. A solution prepared bydissolving oxygen in a 1-M aqueous solution of sulfuric acid at normaltemperature was used as an electrolyte solution.

The electrodes were rotated at a rotational speed of 1,500 rpm, and acurrent when a potential was swept at a sweep rate of 0.5 mV/sec wasrecorded as a function of the potential. In addition, the voltage atwhich a reduction current of −10 μA/cm² flowed in the resultantpolarization curve was recorded as an oxygen reduction-startingpotential. A current density when a voltage of 0.7 V was applied wasalso recorded. Further, the number n of electrons involved in a reactionwas calculated from the following equation (I). In the equation (I),I_(D) and I_(R) represent a disk current and a ring current at apotential of 0 V, respectively, and N represents a capture ratio, whichwas set to 0.372256.

$\begin{matrix}{n = \frac{4\; I_{D}}{I_{D} + \frac{I_{R}}{N}}} & (I)\end{matrix}$

FIG. 2 illustrates an example of a relationship between a voltage and acurrent density obtained by a rotating ring-disk electrode method. FIG.2(A) illustrates the results for the four kinds of Pc/Co catalysts, andFIG. 2(B) illustrates the results for the four kinds of PVP/Fe/KBcatalysts, the Q/Co/KB catalyst, and the Q-Ph/Co/KB catalyst. In FIG. 2,the axis of abscissa indicates a voltage (V vs. NHE) and the axis ofordinate indicates a current density (mA/cm²) at each voltage. It shouldbe noted that in FIG. 2, a carbon catalyst enabling the flow of a largercurrent at a higher voltage means that the catalyst has higherperformance. In addition, FIG. 3 illustrates an example of the resultsof the evaluation of each of the carbon catalysts for its currentdensity (mA/cm²) when a voltage of 0.7 V was applied, oxygenreduction-starting potential (V), and number of electrons involved in areaction.

As illustrated in FIGS. 2 and 3, the oxygen reduction activity of acarbon catalyst can be significantly improved by subjecting the carboncatalyst to a heat treatment. That is, for example, the Pc/Co (H400)subjected to the heat treatment at 400° C. provided a current densityabout five times as high as that of the Pc/Co (N) not subjected to anyheat treatment. In addition, the Pc/Co (H700) subjected to the heattreatment at 700° C. provided a current density about 30 times as highas that of the Pc/Co (N) not subjected to any heat treatment. Further,the Pc/Co (H1000) subjected to the heat treatment at 1,000° C. provideda current density about 42 times as high as that of the Pc/Co (N) notsubjected to any heat treatment.

That is, for example, the carbon catalysts each subjected to a heattreatment at 700° C. or 1,000° C. (PVP/Fe/KB (H700) and PVP/Fe/KB(H1000)) each showed an increase in current density by a factor ofaround 2.5 compared with that of the carbon catalyst not subjected toany heat treatment (PVP/Fe/KB (N)).

It was thought that performing such heat treatment was able toeffectively burn off, for example, a functional group on the surface ofa carbon catalyst, and as a result, a reaction field that could cause anoxygen reduction reaction was efficiently formed at an edge portion of acarbon network plane.

EXAMPLE 5

A raw material containing a polyvinyl pyridine iron complex and ketjenblack, and containing the ketjen black at 50 wt %, was obtained in thesame manner as in Example 1 described above. Then, in the same manner asin Example 1 described above, the temperature of the raw material wasincreased by heating, and then the raw material was held under anitrogen atmosphere at 500° C., 600° C., 700° C., 800° C., 900° C., or1,000° C. for 1 hour.

Further, in the same manner as in Example 1 described above, thecompositions thus obtained were pulverized and sieved, followed by ametal-removing treatment. Thus, six kinds of carbon catalysts subjectedto carbonization treatments at different temperatures (PVP/Fe/KB (C500),PVP/Fe/KB (C600), PVP/Fe/KB (C700), PVP/Fe/KB (C800), PVP/Fe/KB (C900),and PVP/Fe/KB (C1000)) were obtained.

In addition, in the same manner as in Example 1 described above, part ofthe four kinds of carbon catalysts manufactured at carbonizationtemperatures of 700° C. to 1,000° C. were each subjected to a heattreatment. A heating temperature in the heat treatment was set to 700°C. Then, each of the carbon catalysts was evaluated for its oxygenreduction activity in the same manner as in Example 4 described above.

FIG. 4 illustrates an example of the results of the evaluation of eachof the four kinds of carbon catalysts, each of which was manufactured ata carbonization temperature of 700° C. to 1,000° C. but was notsubjected to any heat treatment, and the four kinds of catalysts, eachof which was manufactured at a carbonization temperature of 700° C. to1,000° C. and subjected to a heat treatment for its oxygenreduction-starting potential (V) and number of electrons involved in areaction. As illustrated in FIG. 4, subjecting a carbon catalyst to aheat treatment improved the oxygen reduction activity of the carboncatalyst.

EXAMPLE 6

Two kinds of carbon catalysts each carbonized at 800° C. or 1,000° C. (aPc/Co (C800) catalyst and a Pc/Co (C1000) catalyst) were obtained in thesame manner as in Example 3 described above. In addition, similarly, acarbon catalyst carbonized at 800° C. (Pc/Fe (C800) catalyst) wasobtained by using an iron phthalocyanine complex instead of the cobaltphthalocyanine complex. Then, each of the carbon catalysts was evaluatedfor its oxygen reduction activity in the same manner as in Example 4described above.

FIG. 5 illustrates an example of the results of the evaluation of eachof the carbon catalysts for its current density (mA/cm²) when a voltageof 0.7 V was applied and oxygen reduction-starting potential (V). Asillustrated in FIG. 5, it was confirmed that each of the carboncatalysts had an oxygen reduction activity.

EXAMPLE 7

The eight kinds of carbon catalysts out of the carbon catalysts obtainedin Example 5 described above, the ketjen black used in the manufactureof each of the carbon catalysts, and the three kinds of carbon catalystsobtained in Example 6, were each evaluated for the distribution of theircrystallite sizes La.

A carbon catalyst sample was placed in a concave portion of a glasssample plate, and at the same time, was pressed with a slide glass.Thus, the sample was uniformly loaded into the concave portion so thatits surface and a reference surface might coincide with each other.Next, the glass sample plate was fixed on a wide-angle X-ray diffractionsample base so that the morphology of the loaded carbon catalyst samplemight not collapse.

Then, X-ray diffraction measurement was performed with an X-raydiffraction apparatus (Rigaku RINT2100/PC, Rigaku Corporation). Avoltage and a current applied to an X-ray tube were set to 32 kV and 20mA, respectively. A sampling interval, a scanning rate, and ameasurement angle range (2θ) were set to 0.1°, 0.1°/min, and 5 to 100° ,respectively. CuKα was used as an incident X-ray.

First, the powder X-ray diffraction pattern of each sample was measured.Then, a diffraction peak was measured, and integration was performedfour times. Thus, data to be analyzed was obtained. Next, the average ofthe network plane sizes, and distribution of the sizes, of carbon wereanalyzed by employing Diamond's method. Analytical software (CarbonAnalyzer D series, Hiroyuki FUJIMOTO,http://www.asahi-net.or.jp/˜qn6h-fjmt/) installed in a computer was usedin the analysis. The data to be analyzed was limited to the eleven-bandintensity of a carbonaceous material measured with a CuKα ray as anX-ray source by using a counter graphite monochrometer. In addition, themaximum network plane size that could be analyzed was about 7 nm.

Here, the procedure of the analysis method proposed by Diamond isbasically formed of the following six steps: (1) the measurement of theeleven-band intensity of a sample; (2) the correction of the measuredintensity; (3) the assumption of model network planes expected to existin the sample; (4) the calculation of theoretical scattering intensitiesfrom the assumed model network planes; (5) the least-square fitting ofthe determined measured intensity with the theoretical scatteringintensities; and (6) the calculation of the weight fractions of themodel network planes and an average network plane size from the weightsof the respective theoretical scattering intensities. In view of theforegoing, first, the data to be analyzed was read, and was subjected toa smoothing treatment and absorption correction. The smoothing treatmentwas performed seven times, and the absorption correction was performedwith a theoretical absorption coefficient of 4.219.

Next, the theoretical scattering intensities were calculated. Thefollowing equation (II) was used as a calculation equation. In theequation (II), I represents the measured intensity, w represents a massfraction, B represents a theoretical X-ray scattering intensity, Prepresents a polarization factor, and v and s each represent a networkplane model factor.

$\begin{matrix}{I_{OBS} = {{\sum\limits_{i = 1}^{n}\;{w_{i}{B_{i}(s)}}} + {B^{{{- {CH}}\; 2} -}(s)} + {B^{{- {CH}}\; 3}(s)} + {B^{{- {NH}}\; 2}(s)} + {B^{{> C} = O}(s)} + {B^{{- O} -}(s)} + {\sum\limits^{\;}\;{P_{r}(s)}} + {v(s)}}} & ({II})\end{matrix}$

Here, all parameters can each be represented as a function of n (seeHiroyuki FUJIMOTO, Carbon, 192 (2000) 125-129). The calculation of thetheoretical scattering intensities requires the determination of atwo-dimensional lattice constant a₀ and a Ruland coefficient, and theselection of the model network planes as the setting of initialconditions. The two-dimensional lattice constant is generally set to avalue between the lattice constants of benzene and ideal graphite, i.e.,about 0.240 to 0.24612 nm. The Ruland coefficient represents theintegration width of a function showing the pass band of the energy ofthe monochrometer used, and generally takes a value of 0 to 1.

In this analysis, 0.24412 nm, a value close to the lattice constant of ageneral carbonaceous material, was selected as the initially set valueof the lattice constant a₀, and 0.05 was selected as the initially setvalue of the Ruland coefficient.

Next, the model network planes were selected. The above-mentionedsoftware can execute the calculation of a theoretical intensity withthree kinds of model network planes, i.e., a benzene-coronene basemodel, a pyrene base model, and a mixed model. In contrast, abenzene-coronene base model such as illustrated in FIG. 6 was used inthis analysis. In the case of the model, the scattering intensity of amodel network plane having a size of an odd-number multiple (x1, 3, 5, .. . , 25, 27, or 29) of the two-dimensional lattice constant a₀ (thatis, the size is about 0.25 nm to 7 nm) can be calculated.

Thus, all selection conditions were determined, and then the theoreticalscattering intensities were calculated. After the completion of thecalculation, repeated calculation according to the least-square methodbased on the following equation (III) was performed 1,000 times. Then, ameasured profile and a theoretical profile were fitted with each otherwith a fitting angle range 2θ set to 60 to 100°. After the completion ofthe fitting, the display of the computer displayed a fitting result, anetwork plane size distribution, and an average network plane size.Thus, the ratios (%) of crystallite sizes of 0.245 nm, 0.736 nm, 1.223nm, 1.719 nm, 2.210 nm, 2.700 nm, 3.200 nm, 3.683 nm, 4.174 nm, 4.665nm, 5.156 nm, 5.647 nm, 6.138 nm, 6.630 nm, and 7.110 nm were obtainedas the distribution of the crystallite sizes La of 7.2 nm or less.

$\begin{matrix}{{❘R} = {\frac{\sum\limits_{S}^{\;}\;{{I_{OS} - {\sum\limits_{i}^{\;}\;{\lambda_{i}B_{is}}}}}}{\sum\limits_{S}^{\;}\; I_{OS}} \times 100}} & ({III})\end{matrix}$

FIG. 7 illustrates an example of the distribution of the crystallitesizes La obtained for each of the eight kinds of carbon catalystsmanufactured at carbonization temperatures of 700 to 1,000° C. inExample 5 described above and the ketjen black used in the manufactureof each of the carbon catalysts. FIGS. 7(A), 7(C), 7(E), and 7(G)illustrate the results of the carbon catalysts which were manufacturedat carbonization temperatures of 700° C., 800° C., 900° C., and 1,000°C. but were not subjected to any heat treatment, respectively. FIGS.7(B), 7(D), 7(F), and 7(H) illustrate the results of the carboncatalysts which were manufactured at carbonization temperatures of 700°C., 800° C., 900° C., and 1,000° C. and subjected to a heat treatment at700° C., respectively. FIG. 7(I) represents the results of the ketjenblack.

In addition, FIG. 8 illustrates an example of the distribution of thecrystallite sizes La obtained for each of the three kinds of carboncatalysts obtained in Example 6 described above. FIGS. 8(A), 8(B), and8(C) illustrate the results of the Pc/Co (C800) catalyst, the Pc/Co(C1000) catalyst, and the Pc/Fe (C800) catalyst not subjected to anyheat treatment, respectively. In addition, FIG. 9 illustrates the ratio(%) of the crystallite sizes La in each range in the distribution of thecrystallite sizes La obtained for each of the thirteen kinds of carboncatalysts and the ketjen black serving as the objects of the analysis.

As illustrated in FIGS. 7 to 9, of the ten kinds of carbon catalysts(PVP/Fe/KB) manufactured by using raw materials each containing thepolyvinyl pyridine, iron, and the ketjen black, the carbon catalystssubjected to the heat treatment each had a distribution of thecrystallite sizes La different from that of the carbon catalyst notsubjected to any heat treatment.

That is, for example, the PVP/Fe/KB catalysts subjected to the heattreatment each had such a specific distribution of the crystallite sizesLa that the ratio of the crystallite sizes La in the range of 2 to 5 nmwas as high as 80 to 100% and the ratio of the crystallite sizes of lessthan 2 nm was as low as 10% or less. Further, the PVP/Fe/KB catalystssubjected to the heat treatment each had such a specific distribution ofthe crystallite sizes La that the ratio of the crystallite sizes La inthe range of 3 to 5 nm was as high as 70% or more and the ratio of thecrystallite sizes of less than 3 nm was as low as 20% or less.

Such change of the distribution of the crystallite sizes La of a carboncatalyst depending on the presence or absence of a heat treatment wasconsidered to be related to such improvement in oxygen reductionactivity brought about by the heat treatment as illustrated in FIG. 3 ofExample 4 described above.

The invention claimed is:
 1. A carbon catalyst comprising: a carbonstructure; and a fine metal particle, wherein: the carbon structure isformed of a carbon network plane in which, in a distribution ofcrystallite sizes La of 7.2 nm or less, a ratio of crystallite sizes of1 to 5 nm is 10% or more, a ratio of crystallite sizes in excess of 5 nmis 60% or less, a ratio of crystallite sizes of 2 to 5 nm is 80% ormore, and a ratio of crystallite sizes of less than 2 nm is 10% or less;and the carbon catalyst has a turbostratic structure including a layeredlaminated structure like an onion around the fine metal particle.
 2. Thecarbon catalyst according to claim 1, wherein, in the distribution ofthe crystallite sizes La, a ratio of crystallite sizes of 3 to 5 nm is70% or more, and a ratio of crystallite sizes of less than 3 nm is 20%or less.
 3. The carbon catalyst according to claim 1, wherein the carbonstructure comprises a carbon structure formed by heating a raw materialcontaining a resin and a metal to carbonize the resin.
 4. An electrodethat carries the carbon catalyst according to claim
 1. 5. A batterycomprising the electrode according to claim
 4. 6. A carbon catalystcomprising: a carbon structure; and a fine metal particle, wherein: thecarbon structure is formed of a carbon network plane in which, in adistribution of crystallite sizes La of 7.2 nm or less, a ratio ofcrystallite sizes of 1 to 5 nm is 10% or more, a ratio of crystallitesizes less than 1 nm is 70% or less, a ratio of crystallite sizes of 2to 5 nm is 80% or more, and a ratio of crystallite sizes of less than 2nm is 10% or less; and the carbon catalyst has a turbostratic structureincluding a layered laminated structure like an onion around the finemetal particle.
 7. The carbon catalyst according to claim 6, wherein, inthe distribution of the crystallite sizes La, a ratio of crystallitesizes of 3 to 5 nm is 70% or more, and a ratio of crystallite sizes ofless than 3 nm is 20% or less.
 8. The carbon catalyst according to claim6, wherein the carbon structure comprises a carbon structure formed byheating a raw material containing a resin and a metal to carbonize theresin.
 9. An electrode that carries the carbon catalyst according toclaim
 6. 10. A battery comprising the electrode according to claim 9.11. A carbon catalyst comprising: a carbon structure; and a fine metalparticle, wherein: the carbon structure is formed of a carbon networkplane in which, in a distribution of crystallite sizes La of 7.2 nm orless, a ratio of crystallite sizes of 1 to 5 nm is 10% or more, a ratioof crystallite sizes in excess of 5 nm is 60% or less, a ratio ofcrystallite sizes of 3 to 5 nm is 70% or more, and a ratio ofcrystallite sizes of less than 3 nm is 20% or less; and the carboncatalyst has a turbostratic structure including a layered laminatedstructure like an onion around the fine metal particle.
 12. The carboncatalyst according to claim 11, wherein the carbon structure comprises acarbon structure formed by heating a raw material containing a resin anda metal to carbonize the resin.
 13. An electrode that carries the carboncatalyst according to claim
 11. 14. A battery comprising the electrodeaccording to claim
 13. 15. A carbon catalyst comprising: a carbonstructure; and a fine metal particle, wherein: the carbon structure isformed of a carbon network plane in which, in a distribution ofcrystallite sizes La of 7.2 rim or less, a ratio of crystallite sizes of1 to 5 rim is 10% or more, a ratio of crystallite sizes less than 1 nmis 70% or less, a ratio of crystallite sizes of 3 to 5 nm is 70% ormore, and a ratio of crystallite sizes of less than 3 nm is 20% or less;and the carbon catalyst has a turbostratic structure including a layeredlaminated structure like an onion around the fine metal particle. 16.The carbon catalyst according to claim 15, wherein the carbon structurecomprises a carbon structure formed by heating a raw material containinga resin and a metal to carbonize the resin.
 17. An electrode thatcarries the carbon catalyst according to claim
 15. 18. A batterycomprising the electrode according to claim 17.